1. Technical Field of the Invention
The present invention relates to a heating plate for heating a body to be heated and to a process for producing the same.
2. Description of the Related Art
Soaking heating plates to be used for making the temperature distribution, in the widthwise direction in, for example, a fixing roll in an electronic copying machine, uniform have hitherto been disclosed (for example, see JP-UM-A-58-154378 (FIG. 1)).
In one example shown in FIG. 12, a heating plate 1 has a metal plate 2 having, for example, a rectangular cross-sectional shape and made of aluminum, etc., and plural communicating holes 3 are bored in parallel to a front surface 2b or a rear surface 2c from a side surface 2a of the metal plate 2. In each of the communicating holes 3, a capillary structure (wick) 4 is inserted into the communicating hole 3 while making the internal surface of the communicating hole 3 work as a pipe, and a non-illustrated working fluid is vacuum charged in the wick 4, thereby forming a so-called heat pipe.
Accordingly, if a portion where a temperature difference is caused in heating the metal plate 2 is present, in the portion where the temperature is high, the heat pipe is heated to vaporize the working fluid, whereby the heat is absorbed to lower the temperature (absorption of latent heat of vaporization), and the vapor moves into the low-temperature portion. In the portion where the temperature is low, the working fluid which has become a vapor is condensed to release the heat, whereby the temperature is increased (release of latent heat of vaporization), and the condensed working fluid moves into the high-temperature portion due to a capillary phenomenon of the wick 4. That is, the vapor whose temperature has become high passes in the central portion of the communicating hole 3 and moves into the low-temperature portion, and the working fluid which has been condensed by releasing the temperature moves into the high-temperature portion along the internal surface of the communicating hole 3. By repeating this cycle, the temperature of the whole of the metal plate 2 is made uniform, thereby achieving heating.
Now, in an image forming device called as a medical imager, which is used in recent years, a print of a visible image is prepared from an image measured by medical instruments such as CT and MRI. In such an image forming device, a photosensitive heat development recording material (hereinafter also referred to as “heat development recording material”) comprising a support (for example, a PET film) having a photosensitive heat development image forming layer formed thereon is used, and a latent image is formed by exposing this heat development recording material with light beams modulated according to image data supplied from an image data supply source (modality) such as MRI. Thereafter, the exposed heat development recording material is thermally developed by a built-in heat development device to cause color development, thereby outputting it as a hard copy. In this case, in order to obtain a stable image, a heating unit capable of uniformly heating the heat development recording material is necessary.
So far, in the heat development device, for the purpose of making the guide surface of a heating section with which the heat development recording material comes into contact uniform, the heat control is carried out while accurately controlling plural heaters, and therefore, this complicated control resulted in an increase in costs. Also, for the sake of absorbing a difference of the heat generation of the plural heaters, it is necessary to increase the heat capacity of the guide itself, and therefore, a heating section was constructed of a metal plate having a thick wall. For this reason, it was difficult to shorten the rise time until the temperature reaches a prescribed development temperature, leading to an obstacle to shortening of the development time.
Then, it may be considered to use the heating plate 1 having soaking properties as disclosed in JP-UM-A-58-154378 (see FIG. 12).
However, in the foregoing heating plate 1, it is necessary to bore plural communicating holes 3 in parallel to the front surface 2b or the rear surface 2c from the side surface 2a of the metal plate 2, and there was encountered such a problem that the processing is difficult, resulting in an increase in costs. Further, there is a disadvantage that the processing precision becomes severe for inserting the wick 4 into the communicating hole 3. Also, although it is possible to form a heating plate having soaking properties by inserting an existing heat pipe into the communicating hole 3, the heat pipe must be brought into intimate contact with the inside of the communicating hole 3. Thus, this case also involved such inconveniences that high processing precision is required in boring processing and that the processing is difficult.